The 2020-2023 Toyota Highlander Hybrid features the latest generation of the brand’s venerable Hybrid Synergy Drive system well proven. Here there is a 2.5-liter Atkinson cycle gasoline engine with D4-S fuel-injection which features both direct and port fuel-injection.
The engine features a relatively high 14.1:1 compression ratio and variable valve timing and can run on regular unleaded fuel or higher. It’s mated to an electric continuously variable transmission with two-motors, one as a main traction motor the other primarily as a starter generator.
It produces a total 243 system horsepower in both FWD models and AWD where an additional electric drive motor is provided at the rear axle. Total system power is limited by software and its high-voltage hybrid battery capacity, not so much the cumulative outputs of its individual components.
Following the airflow, the air-intake charge comes through a snorkel at the top of the radiator to a small air-filter box mounted low on the drive side. From there it flows through a mass airflow sensor and a drive-by wire throttle body into a composite plastic intake manifold.
At the top of the manifold you can see the fuel-injection components for its port fuel-injection but the majority of its direct fuel-injection components are hidden below its composite plastic valve cover. At the top of the engine you can see all four of its spark plug coil packs.
Once the combustion process takes place exhaust exits at the rear of the engine through a tubular exhaust manifold and directly into the catalyst system.
Doing your own maintenance on the Highlander Hybrid is as straight forward as any conventional gasoline model. Stay clear of the bright orange high-voltage wiring as handling it incorrectly can be very dangerous, it’s generally not user servicable anyway.
Checking oil is done at the front center of the engine, the bright yellow dipstick well visible. The oil filler cap is located at the top of the engine valve cover. Both are accessible with the plastic engine sound cover on or off.
Coolant reservoirs for both the engine and hybrid drive system can be found at the passenger side of the engine compartment. The engine coolant reservoir is the one to the left, the hybrid drive system coolant to the right. They both use the same type of coolant.
The brake fluid reservoir can be found at the driver side near the strut tower, remotely located from the electronically controlled brake motor unit. Adjacent to it is the main engine ECU. Just ahead of both is the main fuse panel which can be easily accessed with a fuse removal tool just inside.
The main engine air filter box is located at the front driver side of the engine compartment. Changing the filter can be done easily without tools. The windshield washer fluid reservoir is found just ahead of the main air filter box.
Looking around the engine compartment you will notice there is no 12V battery located here, you will find it behind an access panel in the rear cargo compartment. Also notable is the large electric cooling fan at the radiator, watch your hands when working under the hood even when the engine is powered off.
